I got one of mine (power gear system) to stop leaking with a temporary fix. It was a consistent leak. I could wipe down the exposed ram and then see a small line of fluid slowly running down the ram. This jack had been weeping for a while, but then got worse.

I was ready to remove the jack and take it to a local hydraulic shop for repair, but I needed to make a trip and did not have time to do the repair. Knowing that auto brake fluid will swell gaskets designed for petroleum based fluids, I did the following:

I fully extended the jacks, and wiped down the leaking jack's ram with a clean rag. I then coated the ram (thick coating) with auto brake fluid, and retracted the jack. After letting it sit for 15 minutes, I repeated this process.

We've now made three trips without any leak. If it starts leaking again, then I'll remove and repair.

As per another suggestion in this forum, I decided to try the transmission sealer before rebuilding my leaking Power Gear jack.
There was a slow leak down the ram alternating between the rear jacks when extended. They did't seem to both leak at once.
This is on a 2001 F53 Triton V10 chassis.
I replaced the ATF fluid (per mfg instructions) in the reservoir but added 16oz of "White Shepherd Automatic Transmission Sealer" in place of the last 16oz of ATF. I then cycled the jacks 6 times before completing the process. No leaks so far for about one month. We full-time in our MH so the jacks are down much of the time. To me it was worth a try before rebuilding. Good luck!